Ventricular Fibrillation
A life-threatening chaotic heart rhythm that stops blood flow
Quick Facts
- Type: Cardiac emergency (arrhythmia)
- Effect: Heart stops pumping blood
- Emergency response: Call emergency services, start CPR, use an AED
- Definitive treatment: Defibrillation (electric shock)
Overview
Ventricular fibrillation is a dangerous, abnormal heart rhythm in which the heart's lower chambers (the ventricles) quiver chaotically rather than contracting in a coordinated way. Because the ventricles normally pump blood to the body and lungs, this quivering means the heart effectively stops circulating blood. Within seconds, the person loses consciousness, and without treatment the situation is fatal.
Ventricular fibrillation is the most common cause of sudden cardiac arrest. It is a medical emergency that requires immediate action: calling emergency services, starting CPR, and delivering an electric shock with a defibrillator as quickly as possible. Fast bystander response dramatically improves the chance of survival.
Symptoms
Ventricular fibrillation causes a sudden collapse. The signs are dramatic and unmistakable:
- Sudden loss of consciousness and collapse
- No pulse
- No normal breathing, or only gasping
- No response to being spoken to or touched
Some people have warning symptoms in the minutes before, such as chest pain, dizziness, shortness of breath, palpitations, or fainting, though many collapse without warning. If someone suddenly collapses and is unresponsive and not breathing normally, call emergency services immediately, begin CPR, and use an automated external defibrillator (AED) if one is available.
Causes
Ventricular fibrillation usually arises from a problem with the heart's electrical system, often in the setting of heart disease. Common causes and triggers include:
- Heart attack: The most common cause, when reduced blood flow damages heart muscle and disrupts its electrical signals.
- Existing heart disease: Such as a weakened or enlarged heart muscle (cardiomyopathy).
- Previous heart attack with scarring
- Severe imbalances: In body chemistry, such as potassium levels.
- Inherited rhythm disorders: Certain genetic conditions affecting the heart's electrical channels.
- Electrocution or a severe blow to the chest
Risk Factors
- A previous heart attack or coronary artery disease
- A weakened heart muscle or heart failure
- A prior episode of ventricular fibrillation or cardiac arrest
- Inherited heart rhythm conditions
- Significant electrolyte imbalances
- Use of certain drugs or substances that affect heart rhythm
Diagnosis
During an emergency, ventricular fibrillation is recognized from the collapse and confirmed on a heart monitor or defibrillator showing the chaotic rhythm. After resuscitation, tests look for the cause and the risk of recurrence:
- Electrocardiogram (ECG): Records the heart's electrical activity.
- Blood tests: Check for heart damage and electrolyte problems.
- Imaging: Echocardiogram and other scans assess heart structure and blood flow.
- Specialized studies: To evaluate the electrical system and guide prevention.
Treatment
Immediate treatment is aimed at restoring a normal rhythm and circulation:
- CPR: Chest compressions keep some blood flowing to the brain and heart until a shock can be given.
- Defibrillation: An electric shock from an AED or defibrillator is the definitive treatment to reset the heart rhythm; the sooner it is delivered, the better the chance of survival.
- Emergency medical care: Medications and advanced support after the heart is restarted.
To prevent future episodes, treatment may include managing the underlying heart disease and, in many survivors, placing an implantable cardioverter-defibrillator (ICD), a device that detects dangerous rhythms and delivers a shock automatically.
Prevention
Reducing the risk of ventricular fibrillation centers on heart health and managing known risks:
- Treating coronary artery disease and other heart conditions
- Following prescribed medications after a heart attack
- Having an implantable defibrillator if recommended for high-risk individuals
- Managing blood pressure, cholesterol, and diabetes
- Not smoking and limiting alcohol
- Learning CPR and how to use an AED, which can save lives in an emergency
When to See a Doctor
Ventricular fibrillation is a medical emergency. If someone collapses, is unresponsive, and is not breathing normally:
- Call emergency services immediately
- Begin CPR with firm, fast chest compressions
- Use an automated external defibrillator (AED) as soon as one is available and follow its prompts
See a doctor promptly if you have warning symptoms such as fainting, palpitations, chest pain, or a family history of sudden cardiac death, so your risk can be evaluated.
Frequently Asked Questions
What happens during ventricular fibrillation?
The heart's lower chambers quiver chaotically instead of pumping, so blood stops circulating and the person collapses and loses consciousness within seconds. Without immediate CPR and a defibrillator shock, it is fatal. It is the most common cause of sudden cardiac arrest.
What should I do if someone collapses from a cardiac arrest?
Call emergency services right away, start CPR with firm, fast chest compressions, and use an automated external defibrillator (AED) as soon as one is available, following its prompts. Acting within the first minutes greatly improves survival. Do not wait, since every minute without treatment lowers the chance of recovery.
How is ventricular fibrillation treated?
The definitive treatment is defibrillation, an electric shock that resets the heart rhythm, given as quickly as possible along with CPR. After the heart is restarted, doctors treat the underlying cause and may place an implantable defibrillator to prevent future episodes. Speed of treatment is the most important factor in survival.
What causes ventricular fibrillation?
It is most often triggered by a heart attack, but it can also result from existing heart disease, a weakened heart muscle, severe electrolyte imbalances, inherited rhythm disorders, or electrocution. Many people who experience it have underlying coronary artery disease. Identifying and treating the cause helps prevent it from happening again.
Can ventricular fibrillation be prevented?
Risk can be lowered by treating heart disease, taking prescribed medications, controlling blood pressure, cholesterol, and diabetes, and not smoking. People at high risk may receive an implantable defibrillator that automatically treats dangerous rhythms. Learning CPR and AED use also helps save lives when an event occurs.
References
- American Heart Association. Ventricular Fibrillation.
- National Heart, Lung, and Blood Institute (NHLBI). Arrhythmia.
- MedlinePlus, U.S. National Library of Medicine. Ventricular fibrillation.
- Mayo Clinic. Ventricular fibrillation.